Heat exchanging structure

ABSTRACT

Provided are heat exchanging structures  12  for use in transferring heat energy between an exchange fluid  22  and a working fluid  14.  An exemplary structure  12  has a face sheet  30,  a back sheet  36  and first and a second interior sheets  32, 38.  The first and second interior sheets  32, 38  are undulant and are bonded to one another at a plurality of interior joints  42.  The first interior sheet  32  is bonded to the face sheet  30  at a face joint  34  and the second interior sheet  38  is bonded to the back sheet  36  at a back joint  40.  A fluid passage  44  is formed between the first and second interior sheets  32, 38.  The exchange fluid  22  circulates about the structure  12  and exchanges heat with the working fluid  14.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present disclosure generally relates to a structure for exchangingheat between fluids and more specifically to such structures used inaerospace applications.

(2) Description of the Related Art

Aerospace propulsion systems such as gas turbines, scramjets and rocketsproduce high temperature gases by burning a fuel and oxidizer mixturefor powering vehicles. After the fuel and oxidizer mixture ignites in acombustion chamber, the high-temperature combustion gases traveldownstream to a drive a turbine, or are exhausted through a nozzle.During the combustion process, the combustion chamber walls encounterextremely high temperatures, which can reduce the chamber's strength.Since some aerospace vehicles utilize the combustion chamber as astructural member, any reduction in strength may compromise the vehicleand/or the mission.

A light weight propulsion system is important for enabling the maximumpayload carrying capacity of an aerospace vehicle. Thick combustionchambers and high density materials add weight to the vehicle and reducethe payload capacity. For small aerospace vehicles it is particularlyimportant to have a durable, light-weight combustion chamber to enablethe vehicle to carry adequate payload.

Combustion chambers made from various materials, coatings, and coolingsystems are known. For example, a ceramic combustion chamber liner, suchas disclosed in United States Patent Application Publication NumberUS20060242965 ‘Compliant metal support for ceramic combustor liner in agas turbine engine’, teaches a liner wall made entirely of ceramicmaterial. A cooled combustion chamber, such as disclosed in unpublishedU.S. patent application Ser. No. 11/843,743 ‘Heat exchanger panel andmanufacturing method thereof using transient liquid phase bonding agentand vacuum compression brazing’, teaches combustion chamber walls havingmilled channels and a bonded cover to allow a coolant to circulatethrough the wall itself. Published United States Patent Application20070029369 ‘Transient Liquid Phase Bonding of Dissimilar Metals’,teaches a method of bonding a structure made of dissimilar materials.

BRIEF SUMMARY OF THE INVENTION

Provided are heat exchanging structures for use in transferring heatenergy between two fluids. An exemplary structure has a face sheet, aback sheet, a first interior sheet, and a second interior sheet. Theinterior sheets are undulant and are bonded to one another at aplurality of interior joints. The first interior sheet is bonded to theface sheet at a face joint and the second interior sheet is bonded tothe back sheet at a back joint. A fluid passage is formed between thefirst and second interior sheets.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an isometric view of an annular combustion chamber formed froma heat exchanging structure according to an embodiment of the presentinvention;

FIG. 2 is an isometric view of a three dimensional, heat exchangingstructure according to another embodiment of the present invention;

FIG. 3 is a fragmented sectional view of the heat exchanging structureof FIG. 1 and FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 3;

FIG. 6 is an alternate embodiment of the sectional view of FIG. 5;

FIG. 7 is sectional view taken along line 7-7 of FIG. 3; and

FIG. 8 is an exploded view of a die set and a formed interior sheet.

DETAILED DESCRIPTION OF THE INVENTION

An annular combustion chamber 10 of the type used in aerospacepropulsion systems is illustrated in FIG. 1. A heat exchanging structure12, also referred to as a structure 12, encloses a working fluid 14,such as a hot combustion gas. In this example, an ambient air stream 16surrounds the structure 12. The structure 12 extends circumferentiallyabout a longitudinal, central axis 18 and may be a constant or varyingdiameter along the axis 18. A manifold 20 allows an exchange fluid 22 toenter and exit the structure 12. A structural joint 24 may be includedat one or more locations to secure adjacent structures 12. In thismanner, combustion chambers 10 or other systems of complex geometriesmay be formed. While an annular structure 12 is illustrated here forbrevity, rectangular, polygonal, elliptical, or other enclosed shapedstructures 12 are similarly contemplated.

Referring now to FIG. 2, a three-dimensional structure 12 with anon-enclosed shape is illustrated. In this particular embodiment, aworking fluid 14, such as a hot combustion gas, is proximate thestructure 12 and an exchange fluid 22 enters and exits the structure 12via a manifold 20. In this embodiment, several, three dimensionalstructures 12 may be joined together to form a combustion chamber 10 orother system for use in aerospace propulsion systems. Of course, planarstructures 12 (not shown) are also possible.

The structure 12 transfers heat from the working fluid 14 to theexchange fluid 22 or vice versa. In other words, the exchange fluid 22functions as a heat sink, absorbing heat from the working fluid 14, or aheat source, providing heat to the working fluid 14. Additionally, eachof the working fluid x14 and exchange fluid 22 may be in a liquid or agas state. In some embodiments, the exchange fluid 22 is fuel.

Now, the various elements of the structure 12 will be discussed indetail with reference to FIGS. 3-5. A face sheet 30 is bonded to a firstinterior sheet 32 at a face joint 34. A back sheet 36 is bonded to asecond interior sheet 38 at a back joint 40. The first interior sheet 32is bonded to the second interior sheet 38 at a plurality of interiorjoints 42. A fluid passage 44 between the first and second interiorsheets 32, 38 forms a grid-like pattern and directs the exchange fluid22 throughout the structure 12. The fluid passage 44 is coupled to amanifold 20, thus allowing the exchange fluid 22 to enter and exit thestructure 12.

In order to form complex shaped combustion chambers 10 or other systems,a structural joint 24, such as a lap joint (shown), butt joint or otherstyle joint is used to bond adjacent structures 12. A side wall 46bonded between the face sheet 30 and back sheet 36 provides furtherstrength and design flexibility.

The face sheet 30 and back sheet 36 are generally featureless and createan aerodynamic surface for directing the working fluid 14 and/or ambientair stream 16. The first and second interior sheets 32, 38 are undulant,having a plurality of convex features or undulations 50 formed in theirsurfaces. Each undulation 50 has an upper rim 52 and a lower base 54.The rims 52 of the first interior sheet 32 are bonded to the face sheet30 at a face joint 34, while the rims 52 of the second interior sheet 38are bonded to the back sheet 36 at a back joint 40. The bases 54 of thefirst and second interior sheets 32, 38 are bonded to each other atinterior joints 42. The undulations 50 may be cup shaped with largerbases 54 as illustrated in FIGS. 3-5, or dish shaped with smaller bases54 as illustrated in FIG. 6; however, other shaped bases 54 may also beused if bondable.

In a preferred embodiment, the materials of the face sheet 30 and firstinterior sheet 32 are different than the materials of the back sheet 36and second interior sheet 38. With different material properties, thestructure 12 can exchange sufficient heat while maintaining adequatestructural strength for aerospace applications. In this regard, it'spreferable to have a material for the face sheet 30 and first interiorsheet 32 with a thermal conductivity that differs from the thermalconductivity of the back sheet 36 and the second interior sheet 38. Mostpreferably, the thermal conductivity of the face sheet 30 and firstinterior sheet 32 material is greater than the thermal conductivity ofthe back sheet 36 and the second interior sheet 38 material. Forexample, a face sheet 30 and first interior sheet 32 made of a Copperbased alloy and a back sheet 36 and second interior sheet 38 made of aNickel based alloy provide excellent heat transfer capability withoutcompromising the strength of the structure 12.

With specific attention now given to FIG. 4, the undulations 50 of thefirst and second interior sheets 32,38 are opposed to one another andbonded at their bases 54 by interior joints 42. The space between theundulations 50 forms an approximately grid shaped fluid passage 44. Thefluid passage 44 can also be seen in FIG. 7. The exchange fluid 22circulates within the fluid passage 44 in multiple directions forenhanced heat transfer. The undulations 50 also form a plurality ofenclosed chambers 56 as best seen in FIG. 5. The chambers 56 are formedbetween the face sheet 30 and the first interior sheet 32, and betweenthe back sheet 36 and the second interior sheet 38. Each of the chambers56 is sealed about the rim 52 at the face joint 34 or back joint 40, andthe exchange fluid 22 cannot enter the chambers 56 because of this seal.The undulations 50 in FIGS. 4 and 5 are cup shaped with larger bases 54,while the undulations 50 of FIG. 6 are dish shaped with smaller bases54. Of course, other undulation 50 shapes may be used as long assufficient rim 52 and base 54 areas are provided for bonding thestructure 12 together.

FIG. 7 schematically illustrates the flow of exchange fluid 22 as itcirculates within the passage 44. The undulations 50 form a grid-likepattern in the fluid passage 44, and the exchange fluid 22 circulates inapproximately orthogonal directions. The exchange fluid 22 eitherabsorbs heat from, and/or provides heat to, the face and back sheets 30,36. The exchange fluid 22 may be in a liquid or a gas state as itcirculates through the fluid passage 44.

The first and second interior sheets 32, 38 are readily formed using adie set as illustrated in FIG. 8. While only the first interior sheet 32is shown, the second interior sheet 38 is similarly formed. A male diehalf 60 has a plurality of spaced pins 62 that are forced into aplurality of complementary pockets 64 in a female die half 66. Byplacing an first or second interior sheet 32, 38 between the dies 60,66, while forcing them together, the undulations 50 are formed. Thecomplementary pins 62 and pockets 64 form cup shaped undulations 50 (seeFIG. 5), while complementary conical features will create cup shapedundulations 50 (see FIG. 6).

With the first and second interior sheets 32, 38 formed as describedabove, the structure 12 is assembled and then bonded together using asuitable bonding method. A transient liquid phase, vacuum compressionbonding method is preferable for bonding different materials. A completedescription of the preferred bonding method is disclosed in publishedUnited States Patent Application 20070029369 ‘Transient Liquid PhaseBonding of Dissimilar Metals’, which is incorporated herein by referenceas if included at length.

The bonded structure 12 is next shaped as required for the aerospacevehicle application. Planar, non-planar, annular or other shapes may becreated by die forming, rolling or other shaping means. Multiplestructures 12 may also be bonded together at structural joints 24 toform the complex shapes required for certain applications.

Other alternatives, modifications and variations will become apparent tothose skilled in the art having read the foregoing description. Thedimensions provided herein are merely exemplary and describe but asingle embodiment of the present invention. Accordingly, the inventionembraces those alternatives, modifications and variations as fall withinthe broad scope of the appended claims.

1. A heat exchanging structure comprising: a face sheet; a back sheet; afirst interior sheet bonded to said face sheet at a face joint; a secondinterior sheet bonded to said back sheet at a back joint; and whereinthe first and second interior sheets are bonded to each other at aplurality of interior joints such that a fluid passage is formed betweenthe interior sheets.
 2. The heat exchanging structure as recited inclaim 1, wherein the first and second interior sheets have undulantsurfaces.
 3. The heat exchanging structure as recited in claim 2,wherein each surface undulation has a rim and a base.
 4. The heatexchanging structure as recited in claim 3, wherein at least one of thesurface undulations is cup shaped.
 5. The heat exchanging structure asrecited in claim 3, wherein at least one of the surface undulations isdish shaped.
 6. The heat exchanging structure as recited in claim 3,wherein each of the face and back joints are disposed at the undulationrims.
 7. The heat exchanging structure as recited in claim 3, whereinthe plurality of interior joints are disposed at the undulation bases.8. The heat exchanging structure as recited in claim 1, furthercomprising a plurality of enclosed chambers disposed between said facesheet and said first interior sheet and between said back sheet and saidsecond interior sheet.
 9. The heat exchanging structure as recited inclaim 8, wherein each enclosed chamber is sealed by one of a face jointor a back joint.
 10. The heat exchanging structure as recited in claim1, wherein the fluid passage is approximately grid shaped.
 11. The heatexchanging structure as recited in claim 10, further comprising amanifold coupled to the fluid passage.
 12. The heat exchanging structureas recited in claim 1, wherein the face and back sheets have differentthermal conductivities.
 13. The heat exchanging structure as recited inclaim 12, wherein the material of the face sheet has a thermalconductivity that is greater than the thermal conductivity of the backsheet material.
 14. The heat exchanging structure as recited in claim13, wherein the face sheet is made of a Copper based alloy material. 15.The heat exchanging structure as recited in claim 13, wherein the backsheet is made of a Nickel based alloy material.
 16. The heat exchangingstructure as recited in claim 13, wherein said first interior sheet ismade of the same material as the face sheet and the second interiorsheet is made of the same material as the back sheet.
 17. The heatexchanging structure as recited in claim 1, wherein the face sheet isnonplanar.
 18. The heat exchanging structure as recited in claim 17,wherein the face sheet is annular.
 19. The heat exchanging structure asrecited in claim 1, wherein the joints are made by a transient liquidphase, vacuum compression brazing method.
 20. The heat exchangingstructure as recited in claim 1, wherein the structure is part of acombustion chamber for an aerospace propulsion system.